An unsaturated polyester resin is used for various purposes, such as a transportation, an electricity, a construction, a civil engineering, a residential building equipment, as a binder resin for a fiber-reinforced molded article reinforced by a glass fiber, a carbon fiber and an organic fiber etc. However, there is a still remaining problem of the warping or water resistance when molding. On the other hand, it is difficult to recycle it because it is a thermosetting resin, there is a problem as to how to treat the mill ends be generated in the molded article after used or at the time of molding. Recently, although a technique for recycling waste molded article by resolving it to monomer is developed, it is still generally treated by a landfull or an incineration. Therefore, there is a problem that carbon dioxide generated by the degradation caused by the microorganism or at the time of the incineration makes it possible to accelerate the global warming by a greenhouse gas.
Although a polyester resin is used in various fields as a composition or a material for modification, for a powder coating, an electrophotographic developer, an adhesive, an ultraviolet cure ink etc., in an environment strictly required for a water resistance or a moisture resistance, there are large number of cases which can not be applicable because there is a case that a blister occurs on a coating film, or there is a case that it is impossible to exercise a primary performance since the hydrolysis of the molecular chain comes about.
The polyester resin is used in various fields for a fiber, a packaging material, fiber-reinforced plastic, a coating material, a adhesive or an electrophotographic developer other then the above mentioned powder coating, electrophotographic developer, adhesive or ultraviolet cure ink, the amount used for their becomes enormous amount. Therefore, the amount of a raw material derived from a fossil fuel as used for these polyester resin, or the amount of carbon dioxide be generated at the time of the incineration treatment of the polyester resin after used, have get to a level which can not ignore.
In recent years, a plastic derived from a raw material obtained by the renewable biomass resources has been actively developed. One of the meaning of the plastic derived from these biomass resources is because a plant absorbs repeatedly the carbon dioxide generated at the time of treating these plastic by the landfill, or at the time of treating them by the incineration, and the biomass resources are recycled so that the amount of carbon dioxide on environment could have substantively little influence, so called carbon-neutral could be put into practice.
However, at present, a polylactic acid based material most actively developed has limited uses because it's water resistance, moisture resistance, chemical resistance and mechanical properties are less than that of the conventional polyester.
As the unsaturated polyester, for example, it is known that the unsaturated polyester used for adduct of rosin and maleic anhydride as a saturated acid (Nonpatent literature 1).
As the saturated polyester, it is known that the saturated polyester used for adduct of rosin and maleic anhydride as a saturated acid (Nonpatent literature 1), there is a description that the above polyester resin has an excellent alkali resistance and acid resistance. Furthermore, as an example, it is known that a reaction product of a long-chain epoxy resin and rosin, three or more—functional epoxy resin and rosin is used as an material of the composition (Patent Literatures 1 and 2).
In the field of an electrophotographic toner which is one of the application of the polyester resin, recently, a toner having a reduced diameter and a narrow particle size distribution is required because of the increasing demand for the high-quality image. A method of producing a toner using a phase inversion phenomenon is known as a method of producing a toner having a reduced diameter and a uniform particle size (Patent Literature 3). This method is carried out by causing the phase inversion by adding an aqueous dispersion liquid to a resin solution made by dissolving a resin into a non-water soluble organic solvent, and thereby emulsifying to form an O/W emulsion, and thereby removing the organic solvent by applying heat to the O/W emulsion with stirring to separate out a resin particle. According to the phase inversion, a process can be simplified to obtain a resin particle having a uniform particle size by using a relatively simple method, and it is possible to improve production efficiency as well as to attain the reduction of cost. Furthermore, it is possible to use a various sort of a resin, and to broaden the application of the obtained resin particle, comparing with a pulverizing method or a suspension polymerization method etc.
Moreover, a method of producing a toner having a reduced diameter using a polylactic acid based resin as a raw material, according to a method of the phase inversion is known (Patent Literature 4).
Further, a method of producing water dispersion using polyester containing carboxyl groups as a raw material, according to a method of the phase inversion is known (Patent Literature 5).